Could it be a vitamin A deficiency? I remember something about a turtle's eyelids being swollen to the point where they cover the eyes and leave slits if they didnt get any vitamin A. And if u say ur friend didn't take good care of it, that may be it. I think a turtle can also get swollen eyes from dirty water. A vet can give vitamin A shots, that might help. Otherwise, feed it lotsa carrots and tomatoes and any vitamin A abundant plant.